An official build of Windows Neptune (a beta version of Windows XP before Windows Whistler), official build number 5111. This build of Windows Neptune has been altered so that you don't need a product key to install the operating system and the timebomb, which is when the operating system stops counting the time, which for Windows Neptune is 444 days after installation (1 year, 2 months and 20 days) has been removed from the installer. However, before you install, on real machine (an actual computer) or VM (e.g. VMWare Workstation 17, VirtualBox), you must set the BIOS date to December 11, 1999 or Setup will fail. You can change the date later on in the set-up program for Windows Neptune. It is severely recommended that you run Neptune in a VM environment (e.g. VMWare Workstation 17, VirtualBox) as Neptune is known to be very unstable and is a version that at the time was under construction. Windows Neptune is based on the Windows NT series, the same series Windows 2000, Windows XP and other beta versions of NT including 4.0 and 5.0. Please make sure to read the note prior to downloading the .iso file and installing Neptune.